A major hazard in vehicle operation is the danger of collision with objects which are in the path of the vehicle, and which might not be immediately detectable by the person operating the vehicle. In particular, a hazard in aircraft operation is the danger of collision with ground structures and low-lying obstacles. Overlooking such obstacles, by the aircraft pilot, could result in a crash or a serious accident. Obstacles which are especially difficult to detect by the pilot are, for example, power lines, communication wires, antennas, towers, and the like, which become practically invisible to the pilot in some conditions. Helicopters, in particular, often fly at low altitudes, where ground structures and wires are common, thus the danger of a crash is greater.
Systems for warning aircraft pilots of obstacles in their flight course are known in the art. Such warning systems are often based on laser light detection and ranging (herein abbreviated LIDAR) assemblies. A LIDAR system scans the flight path in front of the aircraft, with a laser beam, and detects laser reflections from obstacles which are in the observable range of the system. The system alerts the pilot of detected obstacles which lie in the flight path ahead. The pilot then decides on the best way to avoid the obstacles, if necessary.
U.S. Pat. No. 6,723,975, issued to Saccomanno and entitled “Scanner for Airborne Laser System,” is directed to a laser scanner for a LIDAR system, for scanning a field of view of an aircraft and detecting obstacles. The scanner comprises a plurality of condensing optical elements, a plurality of windows, an optical enclosure, a multiple-axis scanning mirror and light detectors. The optical enclosure is formed by the windows and condensing optical elements. A laser energy source is located externally to the optical enclosure. One of the condensing optical elements includes an aperture, such as a hole drilled there through, so that a laser beam, emitted from the laser energy source, can enter the optical enclosure.
Laser energy is emitted from the laser source, and enters the optical enclosure, hitting the scanning mirror. The scanning mirror directs the laser energy through the windows of the optical enclosure to a plurality of targets in a field of view. The laser energy returned from the plurality of targets reenters the optical enclosure through the windows, hitting the laser detectors. The reflected laser beam is used to detect obstacles, such as wires, which may be present in front of the aircraft.
U.S. Pat. No. 6,724,470 issued to Barenz et al. and entitled “Laser Assembly for LADAR in Missiles,” is directed to a two-stage laser beam generating device for a laser-radar (herein abbreviated LADAR) system, for use in target tracking missiles. The device comprises a master oscillator, a laser-fiber coupling lens, a fiber Faraday insulator, an erbium doped fiber amplifier (herein abbreviated EDFA), a diode laser pump, a dichroic mirror, a transmitter fiber and a transmitter. The master oscillator is connected to the Faraday insulator through the laser-fiber coupling lens. The dichroic mirror is placed between the output of the Faraday insulator and a first end of the EDFA. The diode laser pump faces the dichroic mirror, in a manner substantially perpendicular to a line connecting the insulator and the EDFA. A second end of the EDFA is connected to the transmitter through the transmitter fiber.
The master oscillator, which is a microchip laser, emits a laser beam, which passes through the coupling lens, and enters the Faraday insulator. The laser beam emerges from the insulator, passes through the dichroic mirror and enters the EDFA through the first end thereof. The laser diode pump generates radiation, which is deflected by the dichroic mirror, such that it enters the EDFA through the first end thereof. The amplified laser beam emerges from the second end of the EDFA, into the transmitter fiber. The transmitter fiber then directs the laser beam to the transmitter, which directs the laser beam towards a target.
U.S. Pat. No. 4,902,127 issued to Byer et al. and entitled “Eye-safe Coherent Laser Radar,” is directed to a laser radar for transmitting eye-safe laser radiation at a target, and detecting reflected laser radiation there from. The laser radar comprises a solid state laser, optical pumping means, optical resonator means, optical amplifier means, transmitter station means, receiver means, a single transverse mode fiber-optic, combining means and detecting means. The laser is coupled to the optical pumping means. The laser is optically coupled to the optical resonator means and to the optical amplifier means. The transmitter station is optically coupled to the optical amplifier means. The single transverse mode fiber-optic is optically coupled to the receiver means. The detecting means is optically coupled to the combining means.
The laser emits a lasant radiation beam, after being pumped by the optical pumping means. The lasant beam passes through the amplifier before passing through the transmitter. The transmitter illuminates the beam at a target. Reflected radiation from the illuminated target passes through the receiver, and then through the fiber optic. The combining means combines the reflected radiation with a reference coherent lasant radiation. The detector receives the combined radiation from the combiner and detects the differences between the reflected radiation and the reference radiation, the differences being representative of parameters associated with the illuminated target.
U.S. Pat. No. 6,130,754 issued to Greene and entitled “Eyesafe Transmission of Hazardous Laser Beams,” is directed to an apparatus for preventing injury to humans while transmitting a non-eyesafe (i.e., hazardous) laser beam. The apparatus comprises a non-eyesafe laser source, an eyesafe laser source, a delay component, a receiver/transmitter switch, a deflecting mirror, a dichroic mirror, an optical detector and a trigger. The eyesafe laser source is connected to the receiver/transmitter switch. The delay component is electrically connected to the eyesafe laser source and the non-eyesafe laser source. The dichroic mirror is placed in the path of the eyesafe laser beam. The deflecting mirror is placed in the path of the non-eyesafe laser beam. The optical detector is connected to the receiver/transmitter switch. The optical detector is further connected to the trigger, which in turn is connected to the non-eyesafe laser source.
The eyesafe laser source emits an eyesafe laser beam, which is deflected by the dichroic mirror. The non-eyesafe laser source emits a non-eyesafe laser beam, after a delay determined by the delay component. The deflecting mirror deflects the non-eyesafe laser beam so that it passes through the dichroic mirror, on the same optical axis as the eyesafe laser beam. After transmitting the eyesafe laser beam, the transmitter/receiver switch is switched to receiving mode. If the detector detects reflections of the eyesafe laser beam (i.e., reflected off an object located in front of the apparatus), then the optical detector disables the non-eyesafe laser source, through the trigger.